Single-crystal-like optoelectronic-properties of MAPbI<sub>3</sub> perovskite polycrystalline thin films

Giesbrecht, Nadja; Schlipf, Johannes; Grill, Irene; Rieder, Philipp; Dyakonov, Vladimir; Bein, Thomas; Hartschuh, Achim; Müller‐Buschbaum, Peter; Docampo, Pablo

doi:10.1039/c7ta11190h

Cited by 46 publications

(65 citation statements)

References 46 publications

(51 reference statements)

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“…This prediction corresponds well with the prevalence of experimental studies of MAPbI 3 in the literature, in which it has been considered one of the best-performing compositions. 3,25,26 In addition, experiments by Choi et al have shown the particular efficacy of the THTO additive to dissolve Pb, corroborating these BO-guided/DFT-driven predictions. 27 The caliber of the prediction for the mixed halides case is more difficult to evaluate since the experimental community has not yet decided on an optimal composition, probably because the number of options is overwhelming.…”

Section: Discussionsupporting

confidence: 53%

“…Once more, we find that THTO is a superior additive for dissolving ABX 3 . 26,27 It is important to note that the Bayesian search produces a ranked list in which a number of candidates may produce closeto-optimal suggestions that meet the target value within the uncertainty of the methodology. That is true in this case, where four compositions are the highest performers with binding energies within 0.84 kJ/mol (0.2 kcal/mol) of each other, making them essentially inseparable.…”

Section: Discussionmentioning

confidence: 99%

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Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

et al. 2018

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Accelerated searches, made possible by machine learning techniques, are of growing interest in materials discovery. A suitable case involves the solution processing of components that ultimately form thin films of solar cell materials known as hybrid organic-inorganic perovskites (HOIPs). The number of molecular species that combine in solution to form these films constitutes an overwhelmingly large "compositional" space (at times, exceeding 500,000 possible combinations). Selecting a HOIP with desirable characteristics involves choosing different cations, halides, and solvent blends from a diverse palette of options. An unguided search by experimental investigations or molecular simulations is prohibitively expensive. In this work, we propose a Bayesian optimization method that uses an application-specific kernel to overcome challenges where data is scarce, and in which the search space is given by binary variables indicating whether a constituent is present or not. We demonstrate that the proposed approach identifies HOIPs with the targeted maximum intermolecular binding energy between HOIP salt and solvent at considerably lower cost than previous state-of-the-art Bayesian optimization methodology and at a fraction of the time (less than 10%) needed to complete an exhaustive search. We find an optimal composition within 15 ± 10 iterations in a HOIP compositional space containing 72 combinations, and within 31 ± 9 iterations when considering mixed halides (240 combinations). Exhaustive quantum mechanical simulations of all possible combinations were used to validate the optimal prediction from a Bayesian optimization approach. This paper demonstrates the potential of the Bayesian optimization methodology reported here for new materials discovery.

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

et al. 2018

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“…Thus, we suggest that high defect densities in the material due to the not densely-packed nanocrystalline MASI thin film morphologies are responsible for the low photovoltaic efficiencies. Assuming internal quantum efficiencies near unity as observed in MAPbI 3 -based solar cells, possible current densities based on our thin-film absorption are around 9 mA cm −2 (see SI figure 1(d)) [46]. In combination with a voltage of 1 V, which is defined by the energy level alignment of the HTL and ETLs used in this work, device efficiencies of around 6% are probable.…”

Section: Resultsmentioning

confidence: 63%

Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells^*

2020

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The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A 3 M 2 X 9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA 3 Sb 2 I 9 was reported to only crystallize in the 'zero-dimensional' (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA 3 Sb 2 I 9 , based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75% relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.

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“…This hysteresis could be reduced by scraping the film from the substrate and instead measuring randomly oriented powder samples. Generally, increasing grain sizes in MAPbI 3 films has resulted in improvements in critical performance parameters, such as an increase in carrier mobility and charge collection efficiency, [33,34] along with smaller bandgaps, longer lifetimes, Grain size in polycrystalline halide perovskite films is known to have an impact on the optoelectronic properties of the films, but its influence on their soft structural properties and phase transitions is unclear. Unless understood and mitigated, such hysteretic changes at low temperature may limit the use of perovskite solar cells in some specific applications, for example, aerospace applications, which require operation at extremely low temperatures [28] (<200 K).…”

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confidence: 99%

Influence of Grain Size on Phase Transitions in Halide Perovskite Films

Stavrakas

Zelewski

Frohna

et al. 2019

Advanced Energy Materials

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toward the optimization of perovskite thin film growth from simple precursors have improved the efficiency and stability of devices to a high quality standard and low cost, placing them on the verge of commercialization. [1][2][3][4][5][6] Nevertheless, a better understanding of what influences their crystalline structure is needed in order to achieve phase purity, manage defects, and ultimately achieve optimal device performances.The dramatic gain in solar cell device efficiency since 2012 is only one of the features making perovskites stand out among other photovoltaic materials. With a Young's modulus around 20 GPa, [7][8][9][10] perovskites are mechanically softer than most other PV materials such as silicon (>160 GPa), [11,12] GaAs (≈85 GPa), [13] CIGS (≈80 GPa), [14,15] and CdTe (≈40 GPa), [16,17] and their structure has been reported to be prone to light-induced, electric-fieldinduced, and temperature-dependent rearrangements. [18][19][20][21][22][23] The workhorse system studied to date, methylammonium lead iodide (MAPbI 3 ), is in a tetragonal phase (TP) at room temperature, but undergoes a transition to a cubic phase at high temperature (≈330 K) and an orthorhombic phase (OP) at low temperature (≈150 K). Recently, we and others [24][25][26] have reported that the structural rearrangement from TP to OP causes a distinct hysteretic change in optical and transport properties as well as device behavior between heating and cooling cycles. This hysteresis could be reduced by scraping the film from the substrate and instead measuring randomly oriented powder samples. [24] These results provide hints that the thermal stability [27] and phase transition can be influenced by the local environment of the film due to interactions between the material and substrate as well as within the bulk film itself. Unless understood and mitigated, such hysteretic changes at low temperature may limit the use of perovskite solar cells in some specific applications, for example, aerospace applications, which require operation at extremely low temperatures [28] (<200 K).State-of-the-art perovskite films are polycrystalline, which leads to microscale inhomogeneities in a number of properties such as morphology and defect distributions [29][30][31][32] and, in turn, to local variations in the electronic environment for charge carriers. Generally, increasing grain sizes in MAPbI 3 films has resulted in improvements in critical performance parameters, such as an increase in carrier mobility and charge collection efficiency, [33,34] along with smaller bandgaps, longer lifetimes, Grain size in polycrystalline halide perovskite films is known to have an impact on the optoelectronic properties of the films, but its influence on their soft structural properties and phase transitions is unclear. Here, temperature-dependent X-ray diffraction, absorption, and macro-and microphotoluminescence measurements are used to investigate the tetragonal to orthorhombic phase transition in thin methylammonium lead iodide films with grain sizes ranging fr...

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Single-crystal-like optoelectronic-properties of MAPbI₃ perovskite polycrystalline thin films

Abstract: Our understanding of the crystallization process of hybrid halide perovskites has propelled the efficiency of state-of-the-art photovoltaic devices to over 22%.

Cited by 46 publications

References 46 publications

Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells^*

Influence of Grain Size on Phase Transitions in Halide Perovskite Films

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Single-crystal-like optoelectronic-properties of MAPbI3 perovskite polycrystalline thin films

Abstract: Our understanding of the crystallization process of hybrid halide perovskites has propelled the efficiency of state-of-the-art photovoltaic devices to over 22%.

Cited by 46 publications

References 46 publications

Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

Efficient search of compositional space for hybrid organic–inorganic perovskites via Bayesian optimization

Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells*

Influence of Grain Size on Phase Transitions in Halide Perovskite Films

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Single-crystal-like optoelectronic-properties of MAPbI₃ perovskite polycrystalline thin films

Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells^*